The present invention relates to a magnetic thin film that can act as a magnetic core for a magnetic component such as a reactor, transformer, and magnetic head and the like. The present invention also relates to a magnetic component in which this magnetic thin film is formed on top of a semiconductor substrate. The present invention also relates to their manufacturing methods. The present invention also relates to a power conversion device.
In the prior art, the magnetic thin film that is the magnetic core of magnetic components such as reactors, transformers, and magnetic heads, and the like is generally manufactured by methods such as sintering, rolling, plating, and sputtering of magnetic materials.
Depending on the usage of the magnetic component, different magnetic qualities are needed. As a general classification, there are hard magnetic qualities and soft magnetic qualities. In hard magnetic qualities, the B-H quality has an angular hysterisis and has a high coercive force. A magnetic component having these hard magnetic qualities include magnetic recording medium and the like. For soft magnetic qualities, the B-H quality has a small coercive force. Magnetic components having this soft magnetic quality include power source components such as inductors and transformers which need to have low magnetic loss. For the magnetic qualities of these magnetic components used in power source components, they must have a high magnetic permeability and must have low overcurrent loss caused by the magnetic lines of force inside the magnetic body. As a result, for the magnetic materials that form the magnetic components used in power source components, magnetic qualities of a high magnetic permeability as well as a high electric resistance are desired.
For the magnetic qualities of magnetic components used in power source components, a coercive force (Hc) of 40 mA/m or less, a saturation magnetic flux density (Bs) of 1 T or greater, a magnetic permeability (mu) on the order of several thousand (MHz), and an electrical resistance (rho) of 10xe2x88x926/ohm m or greater have been sought. Magnetic components formed from Co type amorphous magnetic thin films formed by sputtering and the like have been implemented.
Referring to FIG. 14, there is shown a structural diagram of a thin film inductor formed on top of a silicon substrate by a sputtering method. Referring to FIG. 14(a), there is a plan view, and referring to FIG. 14(b), there is a cross-section cut along line Axe2x80x94A of FIG. 14(a). This thin film inductor has a thickness of 60 micrometers. It is constructed by sandwiching a planar spiral coil of copper (a Cu coil 104) between a magnetic thin film 103 and a magnetic thin film 106. Magnetic thin film 103 and magnetic thin film 106 are Co amorphous and are formed by sputtering. Referring to the figure, a two-turn coil is shown, but in practice, coils of several turns to several tens of turns are used. Furthermore, referring to the figure, there are a silicon substrate 101 on which an IC or switching element is formed, a polyimide film 102, magnetic thin film 103 of CoHfraPd, a polyimide film 105, magnetic thin film 106 of CoHfTaPd. A connection conductor 107 connects an end part of the central part of Cu coil 104 with the switching element formed on silicon substrate 101. Connection conductor 107 is formed at the same time as when Cu coil 104 is formed.
Referring to FIG. 15, the process for manufacturing the magnetic thin film that is formed by the sputter method is shown. Referring to FIGS. 15(a) to 15(d), there are shown cross sections of the manufacturing process in the process sequence. This is the process for manufacturing the thin film inductor of FIG. 11.
A silicon substrate 81 has a built-in semiconductor element, such as IC or a switching element. After coating and baking a non-photosensitive polyimide 82 (thickness 5 xcexcm) onto silicon substrate 81, a CoHfTaPd film 83 (thickness 9 xcexcm) is formed by a sputter method (FIG. 15(a)). Next, a non-photosensitive polyimide 84 (thickness 5 xcexcm) is again coated and baked. Ti/Au(=0.5/0.1 xcexcm) is formed by a sputter method, and patterning is conducted, and this becomes a plated electrode layer 85 (FIG. 15(b)). At this time, in order to have an electrical connection with the switching element formed on silicon substrate 81, a connection conductor 90 is formed at the same time as the formation of plated electrode layer 85. Next, a photosensitive polyimide film 86 is coated and baked, and patterning is conducted, and a plating mask (thickness 30 micrometers) is formed, and a Cu coil 87 is formed by plating (FIG. 15(c)). Afterwards, a non-photosensitive polyimide 88 (thickness 5 micrometers) is coated and baked. A magnetic thin film 89 of CoHfraPd film (thickness 9 micrometers) is formed by sputter method, and the inductor is completed (FIG. 15(d)). Referring to Table 1, the qualities of an inductor created in this manner is shown.
In this table, the larger the inductance value L and the smaller the direct current resistance Rdc and the alternating current resistance Rac, the better the quality of the inductor.
For the manufacturing method for the magnetic thin film, when the aforementioned sintering or rolling is used, high temperature treatment of around 1000xc2x0 C. is required. As a result, it is difficult to form a magnetic thin film on top of a semiconductor substrate which has a built-in IC (integrated circuit) and the like. Furthermore, when using plating, although manufacture by normal temperature treatment is possible, the control of the film thickness of the magnetic thin film is difficult. As a result, it is difficult to obtain a good magnetic quality. Furthermore, with the sputter method as described above, this is the method that is most generally used. However, the manufacture process is complex, and mass production is difficult. Therefore, the manufacture cost of magnetic components using this magnetic thin film is high. Furthermore, because the speed of growth is slow with the sputter method, making a thick film is difficult.
Stated more concretely, when forming a Co type amorphous magnetic thin film by sputtering, the speed of accumulation is slow (xcx9c2 xcexcm/h). When mass production is considered, 9 xcexcm is the limit for its film thickness. Currently, the magnetic thick film is implemented at this thickness. Even if mass production is not considered, if the thickness is made any greater, there can be cracking and loss due to membrane stress.
In one example of the prior art for the formation of the magnetic film by sputter method, a magnetic metal (Fe, Co, FePt, and the like) and an oxide with a large oxide heat of formation (Al2O3 and the like) are simultaneously sputter deposited. The magnetic thin film has a structure comprising particle masses of magnetic metal granules and insulating non-metals that surround these granules (H. Fujimori: Scripta metallurgica et materialia, 33, 1625 (1995), S. Ohnuma, et al: J. Appl. Phys. 79, 5130 (1996), S. Kobayashi et al: Nihon OuyouJ Jiki Gakkai-shi 20, 469 (1996), S. Olmuma et al: J. Appl. Phys., 85, 4574 (1999), and the like).
This magnetic thin film is called a metal-non-metal granular film. Compared to the usual magnetic thin film, it has a large electrical resistance. In addition, it is know to show excellent soft magnetic qualities in the high frequency region. Here, metal-non-metal granular films refer to films in which magnetic metal granules are dispersed in a resin and the like. The magnetic metal granules are metal particles (magnetic particles of Fe and the like) covered by a non-metal film (an insulating film such as oxide film and the like). Metal-non-metal granular films can also refer to films in which these magnetic metal granules are aggregated.
However, with magnetic thin films formed in this manner, because a sputter method is used, the manufacturing costs are high, and making a thick film is difficult.
Furthermore, in general in the prior art, a magnetic core of a transformer is manufactured by sintering, rolling, plating, sputtering, and the like of magnetic materials. With sintering or rolling, with high temperature treatment of around 1000xc2x0 C., abulky magnetic core is formed. This type is the standard. Transformers are necessary as an insulated switching power source component. In recent years, there has been demand for smaller, thinner, and lighter components. In responding to this demand, this bulky transformer of the prior art has been a large bottleneck. Recently, instead of these bulky transformers, thin film transformers in which a thin film coil is sandwiched between magnetic thin films have been proposed. Referring to FIG. 16, there is a plan view (FIG. 16(a) ) of a thin film transformer of thickness 100 xcexcm that is created on top of a silicon substrate. Referring to FIG. 16b, there is a cross-section along section A-Axe2x80x2. A primary and a secondary planar spiral coil of copper (thickness 30 xcexcm, width 90 xcexcm, spacing 5 xcexcm) are sandwiched by Co amorphous magnetic thin films (thickness 9 xcexcm) that are formed by a sputter method (in the figure, for simplicity, a two turn coil is shown, but in reality, a sixteen turn coil is used). Referring to FIG. 17, a flow diagram of the prior art is shown. A silicon substrate 171 has a built-in semiconductor element. After coating and baking a non-photosensitive polyimide 172 (thickness 5 xcexcm) onto silicon substrate 171, a CoHtTaPd film 173 (thickness 9 xcexcm is formed by sputter method (FIG. 17(a) ). Next, a non-photosensitive polyimide 174 (thickness 5 xcexcm) is coated and baked again, and a Ti/Au film 175 (=0.5/0.1 xcexcm) is formed by sputter method. Patterning is conducted and a plating mask (photosensitive polyimide) 176 (thickness 30 xcexcm) is formed. Cu plating is conducted, and a primary coil 177 is formed (FIG. 17(c) ). Afterwards, the process in FIG. 17(b) is repeated, and a non-photosensitive polyimide 178 (thickness 5 xcexcm), a plated electrode layer 179 of Ti/Au(=0.5/0.1 xcexcm) are formed (FIG. 17d). Furthermore, the process in FIG. 17c is repeated. After coating and baking a plating mask (photosensitive polyimide) 180 (thickness 5 xcexcm), non-photosensitive polyimide film 182 is formed. Similarly, a secondary coil 181 is provided, and a CoHfTaPd film 183 (thickness 9 xcexcm) is formed by sputter method, and the transformer is completed (FIG. 17(e)). The electrical connection part with the coil is omitted, but a contact part is formed. For convenience, the primary and the secondary coils are shown having equal turn numbers, however, if the input output voltage ratio is changed, they can be formed in the same manner with different turn numbers. With this structure of the prior art, the distance between magnetic thin films become large (in the figure, it is 75 xcexcm), and the leakage flux becomes large. The interlinkage flux between the primary and secondary coils is reduced, and as a result, the magnetic bond between them is weakened, and the output from the primary side is not efficiently transmitted to the secondary side. As a result, with the construction of the prior art, in general, the transformer has a low conversion efficiency.
Furthermore, in the prior art, for the lead wires, enamel wires that are covered with enamel are known. With this type of covered wire, in order to maintain electrical insulation even if there is contact between conductors, the wires are covered with an insulating material. However, in recent years, in conjunction with the miniaturization and high density mounting of electrical components, there have been problems with electromagnetic interference. Because the coated wires of the prior are only for electrical insulation, the mutual interference from the magnetic fields created by current flowing in the lead wires cannot be avoided. Therefore, if the lead wires are covered with a film that can act as an electromagnetic shield, this problem can be avoided.
Furthermore, a power conversion device such as a DC-DC converter and the like has a power source module. In this power source module, individual components of switching element, rectifying element, condenser, control IC and magnetic induction components of coil and transformer and the like are formed as a hybrid on top of a printed substrate of ceramic or plastic and the like. The miniaturization of hybrid power source modules has advanced due to technology such as MCM (multi-chip module), and the like. However, the miniaturization of magnetic induction components such as coil and transformer and the like is difficult. Because these take up a large volume, the miniaturization of the power source module is limited. In recent years, with the use of semiconductor technology, there have been reports of examples of thin micro-magnetic elements (coil, transformer) mounted on top of a semiconductor substrate. For example, in Japanese Laid-Open Patent Application Number 8-149626, a planar magnetic inductor component is disclosed. However, using thin film technology, the process for forming a planar magnetic induction component on top of a substrate with a built-in semiconductor integrated circuit is complex and lengthy. Furthermore, when the planar magnetic induction component is formed by a thin film process, the magnetic thin film and the insulating filler material shrink due to heat treatment. With this stress, there can be warping of the substrate, and processing becomes difficult.
The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements.
It is an object of the present invention is to provide a magnetic thin film that is well suited for mass production, can be manufactured easily, can be made into a thick film, has soft magnetic qualities, and is inexpensive. The present invention also provides a magnetic component that uses this magnetic thin film, manufacturing methods for these, and a power conversion device.
In order to achieve the above objective, the following are implemented.
1) A magnetic thin film, comprising:
a resin in which magnetic fine particles are dispersed.
2) A magnetic thin film as described in Item 1), wherein:
the magnetic fine particles contain at least one metal element selected from a group consisting of Fe, Ni, Co, Mn, and Cr.
3) A magnetic thin film as described in Item 1) or 2), wherein:
the resin is a non-photosensitive resin or a photosensitive resin.
4) A magnetic thin film as described in one of Items 1) through 3), wherein:
the resin is an organic magnetic polymer.
5) A magnetic thin film as described in Item 4), wherein:
the organic magnetic polymer is a cross conjugated polycarbene or a conjugated polymer that has a main chain of polyacetylene and polydiacetylene.
6) A magnetic thin film, wherein:
the thin film is constructed from magnetic fine particles, and the fine particles are aggregated so that the fine particles are in contact with each other.
7) A magnetic thin film as described in one of Items 1) through 6), wherein:
the fine particle comprises a magnetic particle and an insulating film that surrounds the perimeter of the magnetic particle.
8) A manufacturing method for a magnetic thin film, comprising:
a process for dispersing magnetic fine particles in a medium;
a process for coating the medium on top of an insulating film;
a process for heat treating and solidifying the medium.
9) A manufacturing method for a magnetic thin film as described in Item 8), wherein:
the medium is a non-photosensitive resin solution or a photosensitive resin solution.
10) A manufacturing method for a magnetic thin film, comprising:
a process for dispersing magnetic fine particles in a medium;
a process for coating the medium on top of an insulating film;
a process for heat treating, evaporating, and removing the medium.
11) A manufacturing method for a magnetic thin film as described in Item 10), wherein:
the medium is toluene.
12) A magnetic component, comprising:
a first magnetic thin film and a second magnetic thin film being magnetic thin films described in one of Items 1) through 7);
the first magnetic thin film being formed on top of a semiconductor substrate via an insulating film;
a thin film conductor being formed in a spiral shape on top of the first magnetic thin film;
a second resin that fills spaces in the spiral thin film conductor;
the second magnetic thin film being formed on top of the thin film conductor and the second resin.
13) A magnetic component as described in Item 12), wherein:
the second resin is a magnetic thin film as described in one of Items 1) through 5).
14) A magnetic component, comprising:
a third magnetic thin film and a fourth magnetic thin film being magnetic thin films described in Item 6);
the third magnetic thin film being formed on top of a semiconductor substrate via an insulating film;
a thin film conductor being formed in a spiral shape on top of the third magnetic thin film;
the third magnetic thin film being formed in spaces in the spiral thin film conductor;
the fourth magnetic thin film being formed on top of the thin film conductor and the third magnetic thin film.
15) A manufacturing method for a magnetic component, comprising:
a first magnetic thin film and a second magnetic thin film being magnetic thin films described in one of Items 1) through 5);
a process for forming the first magnetic thin film on top of a semiconductor substrate via an insulating film;
a process for forming a thin film conductor in a spiral shape on top of the first magnetic thin film;
a process for filling a second resin in spaces in the spiral thin film conductor;
a process for forming the second magnetic thin film on top of the thin film conductor and the second resin.
16) A manufacturing method for a magnetic component as described in Item 15), wherein:
the second resin is a magnetic thin film described in one of Items 1) through 5).
17) A manufacturing method for a magnetic component, comprising:
a third magnetic thin film and a fourth magnetic thin film being magnetic thin films described in Item 6);
a process for forming the third magnetic thin film on top of a semiconductor substrate via an insulating film;
a process for forming a spiral-shaped thin film conductor on top of the third magnetic thin film;
a process for forming the third magnetic thin film in spaces in the spiral-shaped thin film conductor;
a process for forming the fourth magnetic thin film on top of the thin film conductor and the third thin film.
18) A magnetic component, comprising:
a first magnetic thin film and a second magnetic thin film being magnetic thin films described in one of Items 1) through 5);
the first magnetic thin film being formed on top of an insulating substrate via an insulating film;
a thin film conductor being formed in a spiral shape on top of the first magnetic thin film;
a second resin filling spaces in the spiral-shaped thin film conductor;
the second magnetic thin film being formed on top of the thin film conductor and the second resin.
19) A magnetic component as described in Item 18), wherein:
the second resin is a magnetic thin film as described in one of Items 1) through 5).
20) A magnetic component, comprising:
a third magnetic thin film and a fourth magnetic thin film being magnetic thin films described in Item 6);
the third magnetic thin film being formed on top of an insulating substrate via an insulating film;
a thin film conductor being formed in a spiral shape on top of the third magnetic thin film;
the third magnetic thin film being formed in spaces in the spiral-shaped thin film conductor;
the fourth magnetic thin film being formed on top of the thin film conductor and the third magnetic thin film.
21) A magnetic component as described in one of Items 12) through 14), wherein:
the magnetic component is a transformer.
22) A magnetic component as described in one of Items 12) through 14), wherein:
the magnetic component is a power conversion device.
23) A lead wire, wherein:
the lead wire is covered with a magnetic thin film described in one of Items 1) through 7).
24) A magnetic component, comprising:
a lead wire as described in Item 23) being used as a coil. 25) A current sensor, comprising:
a magnetic sensor being provided on a lead wire described in Item 23). 26) A magnetic component as described in one of Items 12) through 14), comprising:
an insulating film being between the first magnetic thin film and the thin film conductor and the second resin and between the thin film conductor and the second resin and the second magnetic thin film.
27) A magnetic component as described in one of Items 12) through 14), wherein:
the thin film conductor and the second resin is formed as two layers via an insulating film.
28) A power conversion device, comprising:
a magnetic component, comprising:
a magnetic thin film as described in one of Items 1) through 7) being formed on top of a semiconductor integrated circuit substrate via an insulating film;
a thin film conductor being formed in a spiral shape on top of the magnetic thin film;
a second resin being filled in spaces in the spiral-shaped thin film conductor;
the magnetic component being mounted on top of a wiring substrate;
the magnetic component being resin sealed by a resin in which magnetic fine particles are dispersed.
29) A power conversion device, comprising:
a magnetic component, comprising:
a magnetic thin film as described in one of Items 1) through 7) being formed on top of a semiconductor integrated circuit substrate via an insulating film;
a thin film conductor being formed in a spiral shape on top of the magnetic film;
a second resin being filled in spaces in the spiral-shaped thin film conductor;
the magnetic component being mounted onto a lead frame;
a lead terminal being connected to the magnetic component by a metal thin wire;
the lead terminal and the lead frame and the magnetic component are resin sealed by a resin in which magnetic fine particles are dispersed.
30) A power conversion device as described in Item 28) or 29), wherein:
the thin film conductor and the second resin are formed in two layers via an insulating film.
31) A power conversion device as described in Item 28) or 29), wherein:
an insulating film is formed on top of the thin film conductor and the second resin.
As described above, fine particles of magnetic material are dispersed in a medium of resin or a solvent. This medium is coated, dried, and sintered. With this simple method, a magnetic thin film that is suited for mass production, is easy to manufacture, can be made into a thick film, and has soft magnetic qualities can be manufactured inexpensively. Furthermore, magnetic components using this magnetic thin film and power conversion devices can also be manufactured inexpensively.